# How to change 3 Ph supply frequency?

1. Jan 22, 2012

### bobby2211

Hello,

I would like to know about, How to change the 3 Phase supply frequency smoothly over a wide range(for example 1Hz - 100Hz)?

suggest methods if any exists other than mentioned below :
1)Not using Variable frequency drives
2)Not using MG set

Pl note that i want to know, how to change 3 phase supply frequency, not at the generation side.

Thanks.

2. Jan 22, 2012

### Staff: Mentor

If you are talking low power (e.g., to power an experimental design) then you could synthesize three sinusoids from DC using semiconductor circuits, where it's called a function generator. Quite possibly a stepped approximation to a true sine wave would suffice.

3. Jan 22, 2012

### bobby2211

No its not for experimental use.

And i have clearly mentioned, that i want to know, how to change 3 phase supply frequency?
So do u have any other options for the above question?

4. Jan 22, 2012

### sophiecentaur

See how it's done at either ends of high power AC-DC-AC power links (e.g. UK link with the French network). Or perhaps you are only concerned with relatively low powers. The actual spec would be vital to consider before making a choice.

5. Jan 22, 2012

### bobby2211

Why you talk about low power application?

Yes, i can change 3 phase supply frequency using Motor generator set. Where generator rotor runs at Nr to obtain desired 'f'.
But i dont want to implement it as it is a cumbersome process.

so is there any other method to change supply frequency smoothly?

6. Jan 22, 2012

### Staff: Mentor

May I ask what the industrial application is where you know of a need for this?

7. Jan 22, 2012

### sophiecentaur

You didn't make clear what power you are considering.
I did not suggest a motor generator solution - how would you do that for a 1Hz supply? The generators would need to he MASSIVE.
I was suggesting MAR technology. But 1Hz is an unrealistic suggestion for motors or inverters.

You will not find a system for direct conversion. It will be necessary to go via DC, I am sure.
You still do not specify the Power involved. Is it a secret?

8. Jan 22, 2012

### bobby2211

Firstly i would like thank you for patiently replying to my post.

It deals with high power AC sources.

Yes, that is what i want to perform. i.e. will i be able to convert 50hz 3 ph supply to 1Hz 3 phase supply or 51 or vary smoothly over a range?

Yes you are right generators are massive and i dont prefer them too.

So u say that direct conversion is not possible? or Do u have any idea about direct conversion?

And there is no secret involved my friend and there's nothing to reveal.

Finally it will be helpful if u can give me some more suggestions.

9. Jan 22, 2012

### sophiecentaur

What do you call "High Power" exactly?
10kW
1MW
1GW
??

I can't think of may applications that would require enormous powers at a few Hz. What would you do with 1MW at 1Hz?
Inductances would need to be massive, in any AC equipment - either for generation or use.